One issue is that the vast majority of chargers are 100% only with no indication of other charge points.
I know Luna Cycle advocates the shallower cycle. They sell chargers that are switchable 80/90/100%. Their chargers are about $60 more than a generic charger so I would imagine they only really sell to their customers. People tend to buy either the cheapest possible kit or fully pre-built bike, and if you're looking at the out to door price a smaller battery and cheaper charge are going to be significantly cheaper.

And for many people, the cheaper option isn't necessarily a bad thing. My co-worker purchased an ebike, which he occasionally commutes on. At his usage rate, he'll probably get 5-10 years of service from a standard 100-20% duty cycle.